[serializer] include global proxy in additional context snapshots.

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index 9bce3ef628f71b008474143e978655f14246c69d..6d7f5cab13098a1974dd3abf5c507f7f504888bc 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -7560,7 +7560,16 @@ class V8_EXPORT SnapshotCreator {
   Isolate* GetIsolate();
 
   /**
-   * Add a context to be included in the snapshot blob.
+   * Set the default context to be included in the snapshot blob.
+   * The snapshot will not contain the global proxy, and we expect one or a
+   * global object template to create one, to be provided upon deserialization.
+   */
+  void SetDefaultContext(Local<Context> context);
+
+  /**
+   * Add additional context to be included in the snapshot blob.
+   * The snapshot will include the global proxy.
+   *
    * \returns the index of the context in the snapshot blob.
    */
   size_t AddContext(Local<Context> context);
@@ -7884,11 +7893,22 @@ class V8_EXPORT Context {
       MaybeLocal<ObjectTemplate> global_template = MaybeLocal<ObjectTemplate>(),
       MaybeLocal<Value> global_object = MaybeLocal<Value>());
 
+  /**
+   * Create a new context from a (non-default) context snapshot. There
+   * is no way to provide a global template or global proxy since the
+   * context snapshot already contains a global proxy.
+   *
+   * \param isolate See v8::Context::New.
+   *
+   * \param context_snapshot_index The index of the context snapshot to
+   * deserialize from. Use v8::Context::New for the default snapshot.
+   *
+   * \param extensions See v8::Context::New.
+   */
+
   static MaybeLocal<Context> FromSnapshot(
       Isolate* isolate, size_t context_snapshot_index,
-      ExtensionConfiguration* extensions = nullptr,
-      MaybeLocal<ObjectTemplate> global_template = MaybeLocal<ObjectTemplate>(),
-      MaybeLocal<Value> global_object = MaybeLocal<Value>());
+      ExtensionConfiguration* extensions = nullptr);
 
   /**
    * Returns an global object that isn't backed by an actual context.